Refractive correction is achieved through use of spectacle lenses, contact lenses, corneal refractive surgery and intraocular lens implantation. Contact lenses have evolved from non-gas-permeable rigid lenses which made contact with the sclera and vaulted the cornea, to corneal contact lenses made of gas permeable products, and then to corneal-scleral contact lenses made of hydrogel materials. Hybrid lenses were created to provide the improved optics of rigid lenses with the comfort of soft lenses. Conventional hybrid lenses were configured to have a central rigid zone joined at a radial junction to a peripheral hydrogel zone.
Hybrid lenses of this configuration enjoy commercial success with limitations due to the separation of the two materials at their radial junction, lens flexure and tear stagnation due to a circumferential sealing of the lens against the underlying eye. Advanced manufacturing processes and ultra high gas permeable materials have stimulated a resurgence of fully rigid scleral lens designs. Problems with such designs include time consuming lens fitting, lens flexure, scleral impingement, tear stagnation, persistent mid-peripheral bubbles and difficulty in lens removal due to lens adherence.
US Patent Publication No. 2007/0291224 to Shui Lai discloses a lens having a contiguous soft back surface which is bonded to a contiguous rigid front surface. Such a composite lens presents difficulty due to the loss of integrity of the optics due to irregularities caused by the bonding of the soft material to the rigid material in the optic zone of the lens. Further, the expansion of the soft material upon hydration of as little as 1% is known to create stresses at the surface which stimulate optical distortion and potential separation. Additionally, the soft material is known to inter-penetrate the rigid material with resultant random changes in the index of refraction.
Reports of ideal lens-eye relationships with rigid scleral contact lenses detail the importance of having a clearance of between 10 and 100 microns or more between the posterior lens surface and the anterior corneal surface. Hence, there is no clear need for hydrogel material in the corneal portion of a laminated composite hybrid lens.